8.14 Consider the reactions :
2 S2O32– (aq) + I2(s) → S4 O6 2–(aq) + 2I–(aq)
S2O3 2–(aq) + 2Br2(l) + 5 H2O(l) → 2SO42–(aq) + 4Br–(aq) + 10H+(aq)
Why does the same reductant, thiosulphate react differently with iodine and bromine ?
The average oxidising number (O.N.) of S in is +2.
Being a stronger oxidizing agent than oxidises, in which the O.N. of S is +6. However, is a weak oxidising agent.
Therefore, it oxidises, in which the average O.N. or of S in only +2.5.
As a result, reacts differently with iodine and bromine.